EFFECTS OF COLOR AND COLORED LIGHT ON
DEPTH PERCEPTION
A THESIS
SUBMITTED TO THE DEPARTMENT OF
INTERIOR ARCHITECTURE AND
ENVIRONMENTAL DESIGN AND THE INSTITUTE
OF ECONOMICS AND SOCIAL SCIENCES
OF BİLKENT UNIVERSITY
IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS
FOR THE DEGREE OF
MASTER OF FINE ARTS
By
Deniz Atlı
August, 2010
SIGNATURE PAGE
I certify that I have read this thesis and that in my opinion it is fully adequate, in scope
and in quality, as a thesis for the degree of Master of Fine Arts.
Assist. Prof. Dr. Nilgün Olguntürk (Principal Advisor)
I certify that I have read this thesis and that in my opinion it is fully adequate, in scope
and in quality, as a thesis for the degree of Master of Fine Arts.
Prof. Dr. Halime Demirkan
I certify that I have read this thesis and that in my opinion it is fully adequate, in scope
and in quality, as a thesis for the degree of Master of Fine Arts.
Assist. Prof. Dr. Güler Ufuk Demirbaş
Approved by the Institute of Fine Arts
Prof. Dr. Bülent Özgüç, Director of the Institute of Fine Arts
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ABSTRACT
EFFECTS OF COLOR AND COLORED LIGHT ON DEPTH PERCEPTION
Deniz Atlı
MFA in Interior Architecture and Environmental Design
Supervisor : Assist. Prof. Dr. Nilgün Olguntürk
July, 2010
The main purpose of this study is to understand the relationship between different
objects and background colors, and depth perception in interior spaces. The experiment
was conducted in two phases which consist of colored background light pairs (cool
white-orange, cool white-blue, cool white-green, cool white-red, warm white-cool
white, red-green and orange-blue) with colored objects (orange, blue and gray) in front
of them. A forced choice paired comparison method was used to evaluate the differences
in depth perception caused by colors. The participants were students who were having
their internships in Philips Research Eindhoven, Netherlands. Firstly, participants were
tested for color blindness and visual acuity, and the ones who passed these tests
participated in the experiment. After the first phase of the experiment, a second part was
required in order to obtain more accurate results. The participants who had internally
consistent results in the first phase participated in the second phase of the experiment. In
both phases, participants judged the distances of two same colored objects in front of
colored lit background by choosing the one which they perceived as closer to
themselves. As a result, differences between hues are smaller than the variations in
perception of the participants, so hue has a really small effect on depth perception when
evaluated monocularly.
KEYWORDS: depth perception, color, colored lighting.
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ÖZET
RENK VE RENKLİ IŞIĞIN DERİNLİK ALGISINA OLAN ETKİSİ
Deniz Atlı
İç Mimarlık ve Çevre Tasarımı Yüksek Lisans Programı
Danışman : Y. Doç. Dr. Nilgün Olguntürk
Temmuz, 2010
Bu çalısmanın amacı, renkli obje ve renkli arka fon ilişkisinin iç mekanda derinlik
algısına olan etkilerini anlamak ve karşılaştırmaktır. Deney iki aşamalı olarak renkli fon
ışığı çiftlerinin (soğuk beyaz-turuncu, soğuk beyaz-mavi, soğuk beyaz-yeşil, soğuk
beyaz-kırmızı, sıcak beyaz-soğuk beyaz, kırmızı-yeşil ve turuncu-mavi) önünde renkli
objelerle (turuncu, mavi ve gri) gerçekleştirilmiştir. Renklerin derinlik algısı üzerindeki
etkilerini anlamak amacıyla karşılaştırmalı test uygulanmıştır. Katılımcılar, Philips
Araştırma Merkezi, Eindhoven, Hollanda‟da stajlarını sürdürmekte olan öğrencilerden
oluşmaktadır. İlk olarak katılımcılara, renk körlüğü ve görme testleri verilmiştir. Bu
testleri geçenler deneye katılmışlardır. Daha doğru sonuçlar elde etmek amacıyla, birinci
bölümün ardından ikinci bir aşama daha deney yapılmıştır. Birinci aşamada kendi
içerisinde tutarlı sonuçlara sahip olan katılımcılar, ikinci aşamada tekrar teste alınmıştır.
Deneyin iki aşamasında da katılımcılar renkli ışık çiftleriyle aydınlatılmış fonun önünde
iki tane, aynı renkli objenin uzaklıklarını kendilerine daha yakın olarak algıladıkları
objeyi seçmek süretiyle değerlendirmişlerdir. Sonuç olarak, renk türleri arasındaki
farklar katılımcılar arasındaki algı çeşitliliğinden daha küçüktür ve tek göz ile
değerlendirildiğinde renk türünün derinlik algısı üzerinde çok az etkin bir faktör olduğu
söylenebilir.
Anahtar kelimeler: derinlik algısı,renk, renkli aydınlatma.
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ACKNOWLEDGEMENT
Firstly, I would like to thank my supervisors, Ingrid Vogels, Pieter Seuntiens and
Dragan Sekulovski from Philips Research and Assist. Prof. Dr. Nilgün Olguntürk from
Bilkent University for their invaluable support, guidance and encouragement throughout
the preparation of the thesis.
I would like to express my gratitude to my instructors Assoc. Prof. Dr. Feyzan Erkip,
Prof. Dr. Halime Demirkan, Prof. Dr. Mustafa Pultar for their guidance during my
graduate studies. I am grateful to my jury members, Prof. Dr. Halime Demirkan and
Assist. Prof. Dr. Güler Ufuk Demirbaş for their helpful suggestions and valuable
comments.
I would like to thank Philips Research for all the contributions to my thesis and the
entire Visual Experiences Group for the very warm atmosphere. I would like to thank
Gosia Perz who never deprived me of her help during my studies in Eindhoven. I am
grateful to all my friends who did not decline my invitations to be participants in my
longstanding experiments for the thesis. I owe special thanks to my housemates Henry
Huis, David Caicedo, Jerome Perrin and Guillermo Fernandez-Blanco for both their
contribution to my studies and their helpful attitude during my stay in Eindhoven.
I thank Begüm Söker, Seden Odabaşıoğlu, İnci Cantimur, Yaprak Tanrıverdi and İpek
Sancaktar for their support. I owe special thanks to Segah Sak, Elif Helvacıoğlu,
Papatya Dökmeci, Yonca Yıldırım and Burcu Çakırlar for their friendship, patience and
help during these two years. I express my appreciation to my roommate Elif Öztürk for
her endless patience and support.
I express my deepest love and gratitude to my beloved friend Volkan Aykaç and my
parents Özlem Atlı and Behçet Atlı for their invaluable support, trust and
encouragement.
I want to dedicate this thesis to the memory of my invaluable instructor Cengiz Yener
with respect for his guidance and support so that I would be involved in academic
research area. Without his inspiration, I would not be able to start my academic studies
on lighting design.
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TABLE OF CONTENT
SIGNATURE PAGE ........................................................................................................ i
ABSTRACT ..................................................................................................................... ii
ÖZET............................................................................................................................... iii
ACKNOWLEDGEMENT ............................................................................................. iv
TABLE OF CONTENT .................................................................................................. v
LIST OF FIGURES ..................................................................................................... viii
LIST OF TABLES .......................................................................................................... x
1. INTRODUCTION ....................................................................................................... 1
1.1. Aim of the Study .................................................................................................... 2
1.2. Structure of the Thesis ............................................................................................ 2
2. THEORY OF SPACE PERCEPTION...................................................................... 4
2.1. Space Perception .................................................................................................... 4
2.1.1. Parameters of Depth Perception ...................................................................... 5
2.1.1.1. Monocular Depth Cues ............................................................................. 6
2.1.1.2. Binocular Depth Cues ............................................................................. 13
3. COLOR AND LIGHT .............................................................................................. 17
3.1. Color Appearance ................................................................................................. 17
3.1.1. Attributes of Color ......................................................................................... 18
3.1.2. Attributes of Light ......................................................................................... 20
3.1.3. Effects of Light on Attributes of Visual Sensation ........................................ 25
3.1.3.1. Effects on Hue ......................................................................................... 26
3.1.3.2. Effects on Brightness .............................................................................. 28
v
3.1.3.3. Effects on Saturation ............................................................................... 31
3.2. Color in Depth Perception .................................................................................... 32
3.2.1. Effects of Hue, Brightness and Saturation on Depth Perception ................... 33
3.2.2. Effect of Light on Depth Perception .............................................................. 39
4. THE EXPERIMENT ................................................................................................ 42
4.1. Aim of the Study .................................................................................................. 42
4.1.1. Research Questions ........................................................................................ 42
4.1.2. Hypotheses ..................................................................................................... 42
4.2. Method of the Study ............................................................................................. 43
4.2.1. Sample Group ................................................................................................ 43
4.2.2. Experiment Room and Stimuli ...................................................................... 43
4.2.3. Procedure ....................................................................................................... 49
4.2.3.1. Pilot Studies ............................................................................................ 50
4.2.3.2. Forced Choice Paired Comparison Test .................................................. 51
4.2.3.2.1. First Phase ........................................................................................ 51
4.2.3.2.2. Second Phase .................................................................................... 54
4.3. Findings ................................................................................................................ 56
5. DISCUSSION ............................................................................................................ 68
6. CONCLUSION.......................................................................................................... 72
REFERENCES .............................................................................................................. 75
APPENDICES ............................................................................................................... 78
APPENDIX A ............................................................................................................. 79
APPENDIX B.............................................................................................................. 81
APPENDIX C.............................................................................................................. 95
vi
APPENDIX D ........................................................................................................... 115
APPENDIX E ............................................................................................................ 119
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LIST OF FIGURES
Figure 2.1. Graph of different sources of depth information. ........................................... 8
Figure 2.2. Linear perspective cue. ................................................................................... 9
From:http://www1.appstate.edu/~kms/classes/psy3203/MonocularDepth/linear.gif ....... 9
Figure 2.3. Highlights and shadows provide information about depth. .......................... 10
Figure 3.1. Color attributes (Michel, 1996, p.171). ........................................................ 19
Figure 3.2.The CIE 1931 Chromaticity diagram. ........................................................... 24
Figure 3.3. Simultaneous contrast (Achromatic). ........................................................... 30
Figure 3.4. Simultaneous contrast (Chromatic). ............................................................. 30
Figure 3.5. Chromatic aberration. (Sundet, 1987, p.134) ............................................... 34
Figure 4.1. The stimuli with cool white lit background and gray objects. ...................... 46
Figure 4.2. The stimuli with one color combination (red-blue) of background light and
gray object. ...................................................................................................................... 47
Figure 4.3. Experiment room. ......................................................................................... 49
Figure 4.5 Psychometric curves for three participants which are represented one by one
......................................................................................................................................... 58
with baseline and background pair measurements. ......................................................... 58
Figure 4.6. Psychometric curves for three participants which are represented one by one
......................................................................................................................................... 60
with baseline and background pair measurements. ......................................................... 60
Figure 4.7. Psychometric curve for one participant with baseline and background pair 61
measurements. ................................................................................................................. 61
Figure 4.8. Psychometric curves for three participants which are represented one by one
......................................................................................................................................... 63
viii
with baseline and background pair measurements. ......................................................... 63
Figure B.1 Psychometric curves for the combinations (Follow according to Table B.1).
......................................................................................................................................... 83
Figure D.1. Interaction table of object color and background hue pairs ...................... 118
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LIST OF TABLES
Table 4.1. The LCH values of six background colors..................................................... 45
Table 4.2. The LCH and NCS values of three object colors. .......................................... 47
Table 4.3. 35 combinations of object and background colors......................................... 52
Table 4.4. Color combinations evaluated in the second phase. ...................................... 55
Table 4.5. Presentation of which colored object was perceived nearer in front of which
colored background and how many participant perceived difference for each background
pair................................................................................................................................... 67
Table A.1 Sample data list for one participant from phase 2. ......................................... 80
Table B.1 The list of color combinations and psychometric curves of Phase 1. ............ 82
Table D.1.Univariate analysis of variance .................................................................... 116
Table D.2. Post Hoc Tests – Object homogenous subsets ............................................ 117
Table D.3. Post Hoc Tests – Pair homogenous subsets ................................................ 117
Table E.1. Data for first and second phase of the experiment with differences and
significances of the color combinations. ....................................................................... 120
x
1. INTRODUCTION
This thesis concerns color and examines its effects on depth perception as an influential
factor of space perception. Perception is one of the main topics in a lot of research. It
involves immediate and basic experiences of individuals, generated as stimuli, and it
gives them meaning and organization (Matlin and Foley, 1997). One of the observed
and experienced stimuli for individuals is the space which they live in. While
experiencing that physical environment, there are two important physical factors: color
and light, which start up the psychological process of perception. In that sense, the focus
of this thesis is color and light effects on depth perception in interior spaces.
With the emerging technologies, there has been an increase in the use of color and
colored light in both exterior and interior spaces. Especially with the LED technology,
colored and more flexible uses in lighting design fulfill the expectation of individuals by
creating desirable moods, atmospheres and identities of spaces. With different colors
and color combinations of architectural objects and other equipments, different depth
perception cues are obtained, and accordingly, different room size perceptions can be
created. Therefore, it is important to understand the relations between color and colored
light, and depth perception, which is the topic of many critical studies (Mount, Case,
Sanderson and Brenner, 1956; Bailey, Grimm and Davoli, 2006; Ichihara, Kitagawa and
Akutsu, 2007; Huang, 2007).
1
1.1. Aim of the Study
The main purpose of this study is to understand the relation between different objects
and their background colors, and depth perception in interior spaces. In this manner, this
study aims to understand if colored light has an effect on depth perception in interior
spaces and how this can affect depth perception of colored objects.
It is important to understand colored light effects on depth perception because this may
contribute to architectural design of interior spaces. Besides, the findings may be helpful
not only architects but also lighting designers who have the ability to control the light.
1.2. Structure of the Thesis
The thesis consists of six chapters. The first chapter is the Introduction which gives
some information about the topic that the study is going to cover. It gives a brief
explanation of the importance of color, colored light and their relation with depth
perception. The aim of the study and the structure of the thesis are also explained in this
chapter.
The second chapter comprises some basic information on space perception and its
relation with depth perception. Firstly, some definitions on the subject of perception are
explored and an introduction to space perception is made. After that, the depth cues are
categorized under two headings which are monocular and binocular cues, and the
studies conducted on depth cues are explained. In the third chapter, basic terms of color
2
and light which are important for this study are defined. In addition, how light and light
color affect the appearance of colored surfaces is mentioned. Finally, the studies on both
color and light effects on depth perception are reported.
In the fourth chapter, the aim, research questions and hypotheses of the study are
described. The details about the methodology of the experiment are explained in
categories, namely the sample group, description of the experiment room and stimuli,
and the procedure that is conducted through the experiment. The data obtained is
evaluated and the statistical method that is used in the analysis is explained. In the fifth
chapter, the findings are discussed.
The sixth chapter is the Conclusion, which includes the major results of the study, states
the primary outcome observed in the experiment and suggestions for further research
topics.
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2. THEORY OF SPACE PERCEPTION
There have been many definitions and categorizations for explaining the meaning of
perception. It has been expressed as “[…] awareness of objects” by an individual in its
simplest way (Ittelson, 1960, p. 4). In order to find out about the relation between
individuals and their environment, the topic of perception has come into focus as a
research topic for psychologists (Ittelson, 1960). In this manner, perception is explained
as a two-way affair which involves incoming and outgoing channels. This two-way
affair, covering the individual and his/her environment, is referred to as perceiving and
acting, respectively. Besides, “[…] the function of perception is defined as to bring us
into contact with the world outside of ourselves. It is usually stated that this contact is
through our senses.” (Ittelson, 1960, p. 9). According to this approach, the familiar five
senses became a topic of research and as this study is on the appearance of color and
light, it concerns visual perception.
2.1. Space Perception
The world in which an individual lives and sees is made up of three-dimensional
structures, objects and spaces. As perception is one of the aspects that creates the
relation between individual and his/her environment, this three-dimensionality and space
are studied under the title of space perception. Besides, as perception drives through our
4
senses, space perception is investigated under different categories such as, auditory or
visual space perception. In order to understand how an individual experiences the threedimensionality around himself/herself with the influence of color and light, this study
focuses on visual space perception. Specifically, visual space perception is defined as
the ability to perceive the three-dimensional layout of our environment through visual
experiences (Boff, Kaufman and Thomas, 1986). The three-dimensionality encloses the
arrangement of individual particles, each in given size and location. The apparent
location of each particle specifies its direction and distance from the point of view of the
observing eye. In this manner, distance becomes one of the most important attributes of
visual space perception. Since retinal image occurs two-dimensionally in our visual
system, to perceive the distance of an object we need the third-dimension which is
known as depth (Sekular and Blake, 1994). Retinal image uses two angles of line of
sight which specify the position and the size. Besides these two angles, length of line of
sight refers to the third dimension, that is depth (Steven, 1988). To observe distance,
the knowledge of depth cues are studied. With the help of these depth cues, an
individual can conduct three consecutive processes which are detection, discrimination
and identification, to distinguishing objects from each other (Sekular and Blake, 1994).
2.1.1. Parameters of Depth Perception
Depth perception can be defined in two different ways as absolute distance and relative
distance. The distance from an observer to an object is called absolute distance. If the
object distance is considered according to the another, then it is called relative distance
5
(Matlin and Foley, 1983). Differentiation between these two definitions is important to
name the spatial factor that affects an individuals‟ evaluation of distance. Besides, the
location of an object relative to an observer is also defined as egocentric direction,
which is descriptive information for the two-dimensional retinal image dependent on
two angles of line of sight (Sekular and Blake, 1994).
As it is mentioned before, depth perception requires sources of information which are
studied under the name of „cues‟. These cues are studied under two broad categories of
monocular and binocular depth cues (Sekular and Blake, 1994). While remembering
these cues, what the designer must be aware of is how these cues affect the perception of
spatial depth and how they can be used to change the appearance of architectural space.
Monocular depth cues are the ones that can be controlled by a designer more than the
binocular ones when shaping architectural spaces. This is because monocular cues
concern mostly the environmental factors, where binocular depth cues are the ones
which are more physiological in spatial vision and which are affected by the
environmental factors. Both monocular and binocular cues are the attributes that a
designer should be aware of.
2.1.1.1. Monocular Depth Cues
Monocular depth cues, which are also known as pictorial depth cues, can be identified
as relative size, linear perspective, aerial perspective, interposition (occlusion), texture
gradient, light and shade and color (Michel, 1996; Bailey et. al, 2006; Sekular and
6
Blake, 1994; Cutting and Vishton, 1995; Sundet, 1978; Ittelson, 1960). Besides these,
another cue that involves information provided by the eye muscles is accommodation.
These cues of monocular depth perception are the ones that require no movement either
from the object or the observer.
Accommodation in the eye occurs because of the change in the shape of the lens while
focusing on objects at different distances. Thus, eye muscles respond differently towards
the objects at different distances (Matlin and Foley, 1983). However, it has been
mentioned in many sources that accommodation cue can function just for the distances
that are immediately in front of you as it is also represented in Figure 2.1. (Cutting and
Vishton, 1995). From the figure, it can be understood that after nearly 1 m, the effect of
accommodation cue starts to decrease as it gets lower to the assumed utility threshold
for information and after 10 m it has almost no effects. In some other sources, it was
claimed that even for close ranges, “distance judgments based solely on accommodation
are inaccurate” (Sekular and Blake, 1994, p. 218).
7
Figure 2.1. Graph of different sources of depth information. As the distances change, the
effects of cues are also changing. (Cutting and Vishton, 1995, p. 80)
Besides accommodation, when pictorial depth cues are taken into consideration, size is
one of the influencing factors of distance perception. From the Figure 2.1. it can easily
be seen that it has a continuous effect on depth perception. Size and distance are closely
related with each other since the size of the retinal image changes according to the
variation between the observer and the distance of the object (Ittelson, 1960). However,
without any other cue, retinal image may not give the correct size of the object.
Therefore, familiar size and relative size are the effective cues for distance perception
(Sekular and Blake, 1994). When someone always perceives an object according to its
environment some simultaneous effects such as a line looking longer near a shorter one
8
close to it occurs (Gombos and Schanda, 2006). This is the case when a familiar sized
object appears near an unfamiliar one, so an individual can use this clue to detect the
sizes of objects relatively to each other as well as their relative distances. Furthermore,
the farther an object from the observer, the smaller it will appear because the retinal
image that is going to be created will be smaller (Michel, 1996). In this manner, size cue
converges with linear perspective as the appearance of spatial depth becomes
exceptionally strong because of the field of view (Michel, 1996).
The main idea in linear perspective is that parallel lines appear to meet in the distance
while creating a horizon line at the end (Matlin and Foley, 1997). According to linear
perspective cue, the covered portion of the retina gets smaller when the image is closer
to the horizon (and farther from the observer) (see Figure 2.2).
Figure 2.2. Linear perspective cue.
From:http://www1.appstate.edu/~kms/classes/psy3203/MonocularDepth/linear.gif
9
Michel (1996) states that linear perspective is the strongest depth cue which can be used
to create powerful spatial depth. Cook, Yutsudo, Fujimoto and Murata (2008) add that
the density of linear perspective grid lines induces the effect of shadows, texture and
color information of the illusion that are produced on depth perception. With respect to
the linear perspective, the effects on perceiving depth are strongly influenced by the
pictorial cues of shading and shadows of objects on the background and on other objects
(Cook et al., 2008).
Shade and shadows are also important cues for the appearance of three-dimensionality
and solidity of the objects with regard to the degree of darkness of it as well as
perception of depth (Matlin and Foley, 1997; Wyburn, 1964) (see Figure 2.3).
Figure 2.3. Highlights and shadows provide information about depth. The shadows
indicate that the left hand image is convex, whereas the right hand image appears
concave.
From: http://webvision.med.utah.edu/imageswv/KallDepth5.jpg
10
In this manner, the interaction of direction of light and the shape of object produces the
shadow and gives information about the spatial depth as mentioned by Michel (1996).
Light and shade tools play an important role in differentiating foreground and
background from each other and perceiving the spatial layout (Cutting and Vishton,
1995). Shadows can also give crucial data when it is conveyed in relation with another
cue of depth perception such as texture (Michel, 1996; Sekular and Blake, 1994).
Texture gradient is another depth cue that gives clues for the perception of layout and
our environment. “There are at least three gradients of texture in surfaces receding in
depth-depth gradients of size, density and compression” (Cutting and Vishton, 1995,
p.94). Cutting and Vishton (1995) explain the effect of size gradient (the change in the
largest extent of texture element) as similar with relative size which has a continuous
impact on many elements across a surface (see Figure 2.1).
Besides, texture density gradient is defined as the “homogenously distributed markings
[…]” (Steven, 1988, p. 199) and as the distance is increased, the density gets higher in the
visual field. Dissimilarly, according to Cutting and Vishton (1995), the compression
gradient, which refers to the shape of the texture gradient, is ineffective on depth
perception; however, it gives good information about object shape and curvilinearity.
Furthermore, with respect to Palmer and Brooks (2008) experiment, moving, sharp or
red textures (as opposed to stationary, blurred and green) are seen closer.
11
Another cue that is also affected by blurriness and color is aerial perspective. It is the
atmospheric effect that creates another kind of perspective because of the relative
amount of moisture and pollution. Accordingly, with the high degree of these
ingredients, “objects in the distance become bluer and decreased in contrast with respect
to objects in the foreground” (Cutting and Vishton, 1995, p. 88). In a way, distance
causes loss of detail and color in a scene (Steven, 1988). However, this is an effective
depth cue in exterior spaces, not in interiors.
Another cue of depth perception, interposition (occlusion), is mentioned as if an object
appears to overlap with or be a cut off part of another object it tends to appear nearer
(Matlin and Foley, 1997; Wyburn, 1964). Besides, the relative sharpness of outline is
also given as a cue for perceiving depth by Wyburn (1964). Michel (1996) explains this
phenomenon as “when one object or surface is overlapped by another, the one with
continuous outer contour appears to be in front and closer” (p. 25). This is one of the
most important cues of depth; it also has an important role in the binocular disparity
process that will be discussed later in section 2.1.1.2 (Matlin and Foley, 1997).
In addition to all of these cues, Payne (1964) considers color as a cue for distance
perception. He (1964) mentions color as a dependent variable of distance perception
although cues of aerial perspective or light and shade can be considered to be some
characteristics of color. Studies conducted about the effects of color on depth perception
are going to be mentioned broadly later in Section 3.2.
12
2.1.1.2. Binocular Depth Cues
Another set of cues comes from the fact that individuals have two eyes. Besides all the
monocular cues that have been discussed above, there are convergence and divergence,
binocular disparity and color stereopsis cues that can be investigated under the title of
binocular depth cues (Coren, Ward and Enns, 1994).
According to binocular vision, eye movements occur to focus the image on two foveae.
The movements of two eyes towards different direction are called vergence movements.
If this movement is inwards (towards the nose), it is called convergence. The opposite
movement (away from each other), which occurs because the target is farther away, is
called divergence (Coren et. at., 1994). Both the convergence and divergence are
measured by the angles between the optical axes of the two eyes. It is suggested that in
the range of up to only 2 m, convergence can be taken as the only source of information
for depth. Nevertheless, it is not effective enough to perceive distances correctly at great
distances only with convergence (Cutting and Vishton, 1995), Williams and Tresilian
(1999) mention a conflicting result that with the additional depth cues, the contribution
of vergence information becomes complicated. The complexity which is created by the
combinations of cues, can cause unexpected distortions of visual space. For instance, the
distances of objects and points can be perceived closer or further than they actually are.
Moreover, vergence and accommodation are generally noted as cross couple, in the way
that accommodation influences depth perception indirectly via its effect on vergence
(Williams and Tresilian, 1999).
13
Similarly, because individuals have two eyes in which pupils are roughly apart up to 6.5
cm, slightly different images of the environment occur in each eye. The difference
between the two eyes‟ images is called binocular disparity (Coren et.al., 1994). If the
object is in front of the fixation plane, it is crossed disparity because, in order to fixate
on the object, the eyes must cross. However, the objects behind the fixation plane create
uncrossed disparity (Matlin and Foley, 1997). When the distance to the fixation plane
increases, the disparities between the images of two eyes decrease. With all of those
cues, binocular disparity “[…] provides the information needed to judge depth
binocularly, an ability known as stereopsis” (Matlin and Foley, 1997, p. 183). Stereopsis
allows individuals to judge relative depth with great accuracy while making them see
the objects that are invisible to either eye alone (Sekular and Blake, 1994).
Some of the stereoscopic effects are mentioned in Form-And- Color-And- Depth
(FACADE) theory of Grossberg (1994). According to this theory, different depth cues
are investigated interactively under binocular and monocular conditions. According to
the interactions of 3D boundary segmentations of edge, texture, shading and stereo
information with filling-in surface properties of brightness, color and depth, the system
of binocular viewing is analyzed in FACADE theory (Grossberg, 1994). As the main
idea of the theory, pictorial cues are mentioned as activating several types of interaction
processes in cortical mechanism that gives rise to three-dimensional scenic percepts
(Dresp, Durand and Grossberg, 2002).
14
Considering the FACADE theory of Grossberg (1994), studies are focused on the
interaction between interposition and color and texture, in the manner of understanding
the figure-ground separation in depth perception in visual cortex, by examining
binocular conditions. With regard to some of the studies, occlusion provides the most
important cue for depth perception; however, its interaction with different depth cues is
inevitable (Dresp et. al., 2002). Although, Bailey et al. (2006) claim that “perspective
cues such as relative size, occlusion and distance to the horizon are generally more
effective at conveying depth than shading, luminance and colour” (p. 2), Dresp et. al.
(2002) mention that interposition and occlusion on their own are not strong enough to
compete with a strong, conflicting contrast cue. Thus, “interposition and partial
occlusion contribute to generate perceived depth when combined with a cooperative
contrast cue” (Dresp et al., 2002, p. 273). Likewise, Dresp and Guibal (2004) report that
partial occlusion and interposition compete with luminance contrast of red color and
achromatic contrast. Besides luminance, color and contrast interactions with occlusion,
texture is also studied as another component of FACADE theory. Kawabe and Miura
(2006) stat that the texture edges of interposition or occlusion contribute to depth
perception. In their experiment (2006), which indicates the two cues of occlusion and
texture together, it is mentioned that the image with textures of random stripes is seen
nearer than the textured image of constant stripes.
Additionally, due to the effect of color in binocular vision, differences in depth
perception occur and it is known as color stereopsis, which acts as another binocular cue
15
of depth perception (Matlin and Foley, 1997). These differences can occur depending on
the brightness, saturation and hue attributes of color. Furthermore, color stereopsis is
also studied considering figure-ground relations which affords opposite effects on depth
perception (Dengler and Nitschke, 1993). Those effects of color are discussed in detail
in Section 3.2.
16
3. COLOR AND LIGHT
In this section, general definitions of color and light are given. Basic terms determining
color and its attributes, besides light and its effect on color, are focused on. After the
definitions, color and light effects on depth perception are going to be discussed in
detail.
3.1. Color Appearance
In this section, the definitions of color appearance in visual perception are presented in
order to understand the fundamental scientific concepts of color. Color appearance is
generally considered together with the parameters of hue, saturation and brightness of
the visual stimuli that are displayed in the observer‟s field of view. The colored visual
stimulus that is observed by the viewer is specified by the physical details of spatial
properties (size, shape, and location in the visual field) and temporal properties (steady
state, moving, pulsing) and their radiant power distributions (spectral power
distribution) (Boff et al. et al., 1986). The color appearance of the visual stimulus
derives from the experience that the observer gets and the judgment of color appearance
is directly influenced by the conditions and the environment that the visual stimuli are
presented in. Nevertheless, expressing the perceived stimulus has a complicated nature
in itself; therefore, there are some mathematical models designed to describe the color
appearance precisely and universally.
17
According to the Commission International de l’Éclairage (CIE), color can be defined
as an “attribute of visual perception consisting of any combination of chromatic or
achromatic content” (Fairchild, 2005, p. 84) which can be named by chromatic colors as
yellow, orange, green etc. or achromatic colors as white, gray, black etc., and it can be
defined by the adjectives of dim, light, dark etc. Besides, perceived color depends on
“the spectral composition of the radiant energy concerned by the observer” (Boff et al.,
1986, p. 9-2) according to the size, shape and surrounding of the stimulus areas. These
stimulus areas can be both compared to each other as related colors or can be just
judged as unrelated colors in which the circumstances will differ, and so their
appearance will also differ from each other. Moreover, it is important to notice the
difference between the more specified uses of related colors as object color, surface
color and light color. In this research, both the use of surface and light colors are going
to carry importance.
3.1.1. Attributes of Color
As it was defined before, color mainly deals with three basic attributes called hue,
brightness and saturation (Fairchild, 2005) (see Figure 3.1).
18
Figure 3.1. Color attributes (Michel, 1996, p.171).
Referring to the literature according to their use and concepts, instead of brightness,
lightness can be used or instead of saturation, chroma can be used to identify colors.
However, in some research these words mean different impositions with regard to the
conditions and designs of the research.
Firstly, hue is used as an attribute of visual sensation to characterize the name of colors
as red, yellow, green and blue which cannot be described other than its own
(Fairchild,2005). These four colors are the unique hues that are used in combinations to
name the hueness of the other color stimulus like orange (yellowish red or reddish
yellow) (Boff et al., 1986). Hue is also understood as the variation in color when the
wavelength is changed (Padgham and Saunders, 1975).
Secondly, brightness is the aspect of visual sensation which determines the level of
emitted light from an area (Fairchild, 2005). It is also defined as the variations in
perception with the change in intensity (Michel, 1996; Boff et al., 1986). These variation
19
ranges in brightness can be from very bright to very dim. Although in some cases
lightness is used as brightness, the specific definition of it is “the brightness of an area
judged relative to the brightness of a similarly illuminated area that appears to be white
or highly transmitted” (Fairchild, 2005, p. 86). In this sense, lightness can be referred to
as relative brightness.
Additionally, the terms saturation and chroma are perhaps the most contentious in the
literature of color appearance. Chroma is one of the factors in color appearance which
involves a judgment between a chromatic color and an achromatic color of the same
lightness (Boff et al., 1986). It is the “colorfulness of an area judged as a proportion of
brightness of a similarly illuminated area that appears white or highly saturated”
(Fairchild, 2005, p.87). It can be called the relative colorfulness; it approximately stays
constant across the changes of luminance levels on the surfaces or objects which have
the same hue. Saturation can be defined as relative colorfulness as well; however, it is
relative to its own brightness, where chroma is “the relative to the brightness of a
similarly illuminated area that appears white.” (Fairchild, 2005, p. 88). At the same time
saturation “[…] permits a judgment to be made of the degree to which a chromatic color
differs from an achromatic color regardless of their lightness” (Boff et al., 1986, p. 9-4).
3.1.2. Attributes of Light
As an effective factor in color, basic knowledge of light should also be mentioned in
order to have the right explanations of visual perception and color appearance. Light is a
20
form of radiant energy which generates a range of electromagnetic spectrum
(Zukauskas, Shur and Gaska, 2002). The visible radiant energy occupies a small part of
this electromagnetic spectrum which is called visible spectrum. Essentially, the light
range of the spectrum is the only range of the electromagnetic spectrum which acts like
stimuli for the visual system to respond (Zukauskas et. al, 2002). The electromagnetic
radiation is generally defined with a wavelength whose unit of length is nanometer
(nm). The visible light spectrum includes the wavelength ranging between 380 and 780
nm. Between these ranges of visible spectrum, there are different hues perceived as light
colors (Valberg, 2005). Light which is made of a single wavelength is called
monochromatic light, which has the maximum saturation of color in the visible
spectrum (Agoston, 1987).
In the real world, most of the light that is perceived is not monochromatic. A light
coming from any lighting source will contain nearly half of the visible spectrum;
however, it will be perceived as one hue because of the amount of that hue in the light.
For example, green beam in 500-550 nm region of spectrum has a larger amount of
green in the light than blue, so it will be perceived to be greener than the light which is
in 400-500 nm region of the spectrum that has larger amounts of blue in it. These
amounts of radiant energy (power) in the visible range of 380-780 nm can be measured
by spectroradiometer in the manner of wavelength interval (portion) of light (Agoston,
1987).
21
The hues in the visible spectrum are called spectral colors. Besides these spectral colors,
there are some other colors that can be experienced but do not exist in any of the
sources‟ spectrum as monochromatic radiation; they are known as nonspectral colors.
This portion of colors has purple, purplish red and a range of colors which are
neighboring red hues. They can be produced by combining the monochromatic colors
(Agoston, 1987).
Light in our environment is not monochromatic all the time, and its characteristics are
related to its source. Every light source has its own rate of radiant energy (power)
emitted in wavelength intervals in the visible range of the spectrum. Each light source
can be evaluated according to its spectral power, which is related to its radiant energy,
and its effect distribution in wavelength intervals. The relation between spectral power
and effect distribution is defined as spectral power distribution which defines the
characteristic of a light source (Valberg, 2005).
There is also a standardization of light sources which is known as illuminants and it is
generated by CIE according to their spectral power distributions. Illuminant A, D65 and
F2 are some of these CIE standardized illuminants which represent a typical
incandescent light, daylight and fluorescent light, respectively (Fairchild, 2005). Each of
these CIE illuminants are also standardized according to their color temperature which
is another descriptive characteristic of a light source. It is a physical characteristic of
light which is referenced from a special type of theoretical light source, known as black22
body radiator. “The black body radiator emits light with intensity and spectral
distribution depending on the temperature of the material” (Valberg, 2005, p. 38) and
this temperature is originally called color temperature. When the temperature of the
radiator increass, the wavelength becomes shorter. The unit of the color temperature is
generated in Kelvin and the visible light begins to appear around 1000 K. A tungsten
filament lamp can be considered to be the closest to black body radiator; however, as it
is generally not possible to obtain the exact required laboratory conditions of black body
radiator in the environment, correlated color temperature is generally used for defining
light sources (Fairchild, 2005). The CCT is the color temperature of a light source that
has almost the same color as the black body radiator.
The CCT is mostly used to define the color of white light and it has its locus on the CIE
chromaticity coordinates, so its values can easily be estimated from there. CIE
chromaticity diagram is an industry standard and a common way of visualizing a
perceived color according to its CIE tristimulus values (see Figure 3.2).
23
Figure 3.2.The CIE 1931 Chromaticity diagram. The outer horseshoe shaped edge
represents the wavelengths of spectral colors. The horizontal axis represents the
x values and the vertical axis represents the y values. Any color inside the
horseshoe shape has its coordinate with x and y values. (Zukauskas et. al, 2002)
Besides correlated color temperature, it is also possible to control different wavelength
components of light in order to create different colors of light with different
chromaticity coordinates (Zukauskas et. al, 2002). Different colors can be created by
producing different spectra. However, the important thing here is to consider that these
different colors of light can have similar CCTs on the CIE chromaticity diagram, while
24
having different x and y values (Valberg, 2005). Therefore, care should be taken when
one specifies a light source by CCT only, which can be very misleading.
To understand all the qualities of light, some other measures of it should also be known
like intensity, illuminance and luminance. Intensity is the amount of radiant energy
transferred per unit area. It is separated into two in light engineering as illuminance and
luminance in order to express the amount of light. Illuminance (lm/m2) tells how much
light flux enters a unit area according to the distance between the source and the
illuminated area. Accordingly, “the luminance (cd/m2) of a surface tells us how much
light reaches the retina from that surface when the object is imaged through the eye
media” (Valberg, 2005, p. 169). These measures also have some effects on the attributes
of color, especially on brightness, which are going to be mentioned in the next section.
As light has the greatest importance on appearance of surface and object colors, the next
section is going to deal with light effects on color and its parameters.
3.1.3. Effects of Light on Attributes of Visual Sensation
Until now the factors and parameters in the environment that affect the individual‟s
visual perception have been discussed. Light is the primary factor which makes all
other parameters visible by reflection, absorption or transmission from the surfaces. All
the other parameters are additional collateral factors that help individuals to understand
their environment and make them perceive their surrounding in detail and with more
information. In that sense, texture, color and shades are the ones which give information
25
about surfaces where size, perspective and occlusion determine some relations among
different surfaces, objects and spaces. As it is mentioned before, those cues are also used
as sources of information interacting with each other. According to the light source and
with different combinations of those cues, different surroundings can be created and
different appearances of colors, and accordingly different appearances of spaces can be
obtained. In this section, characteristics of light source and the surrounding of the
colored object are going to be taken into account and how the appearance of color
changes is going to be discussed. Color has three basic attributes, each of which is
mentioned under a separate title.
3.1.3.1. Effects on Hue
As the surrounding of the observed color stimuli carries importance on how it appears
and is perceived, the below phenomena are important in order to have an idea about the
effects of light and color on each other. This information may also carry importance for
the design of the stimulus in the study.
For the color appearance attribute of hue, a shift occurs after adding white light into a
monochromatic light by making it vary in purity and this phenomenon is known as
Abney Effect. According to this phenomenon, Johnson and Fairchild (2005) mention that
it is not possible to judge hue parameter of color just by its wavelength since its
colorimetric purity changes as the dominant wavelength stays constant. Therefore, in the
26
chromaticity diagram, the straight lines from the white point to the spectral locus are not
lines of constant hue (Fairchild, 2005).
Another similar phenomenon which deals with the changes in hue perception is BezoldBrücke shift. This time the reason of the change in hue is the variation in intensity. This
is also a reasonable effect that displays wavelength of monochromatic light as not the
only indicator of the perceived hue. Padgham and Saunders (1975) claim that with the
increase in luminance, the hue of red becomes yellower and violet becomes bluer.
Bezold-Brücke shift differs from Abney effect in because its validity is just for unrelated
colors which are seen in isolation from other colors. Hunt has proved that this shift is
not valid for related colors which are “[…] perceived to belong to an area or […] seen in
relation to other colors” as cited in Fairchild (2005, p.89).
Pridmore (2007) has conducted some studies concentrating on Abney and BezoldBrücke effects. He notes that this hue shift is an effective factor in perceiving threedimensional object shape in the manner of adding hue and lightness differences to its
color. According to him, these two effects are directly related to each other depending
on the increase in chroma when the lightness gets higher. This is explained with the
combination of these two effects, the physical features of an object becomes more
definite and the object is perceived more three dimensionally; thereby, all three
attributes of color work together to determine the features of the shape of an object.
27
3.1.3.2. Effects on Brightness
One of the parameters that is defined by the Y tristimulus value in CIE system of
colorimetry as luminance level is brightness. In fact, most of the time it is assumed that
brightness is the function of luminance level; however, when Helmholtz-Kohlrausch
effect is taken into consideration, this is not the case. According to HelmholtzKohlrausch effect, there is a change occurring in perceived brightness with the increase
in purity of the colored stimuli when its luminance is kept constant in the photopic range
(CIE, 1988). With reference to this effect, the stimulus appears brighter at a constant
luminance if the saturation is increased (Johnson and Fairchild, 2005). Furthermore,
Fairchild (2005) claims that this effect is also dependent to the hue of stimulus besides
the saturation. Thus, it is less noticeable for yellow than purples.
In addition, another effect on brightness which occurs with changes in the illumination
level is Purkinje shift. According to Purkinje shift, when the light level decreases,
because of the optical ability of the human eye, the peak sensitivity shifts towards the
blue end of the color spectrum (Fairchild, 2005). Purkinje shift is related to the
adaptation of the human eye and receptor cells in the retina. Because of the visual
functioning of rod and cone cells, in low levels of luminance (less than 0.01 cd/m²)
known as scotopic vision, sensitivity to shorterwavelenghts increases (Fairchild, 2005).
Anstis (2002) has conducted experiments on light effects on Purkinje shift, and he
mentions that because of the switch from cone vision to rod vision through darkadaptation, with the visual sensitivity, blue colors look relatively lighter than red colors.
28
Another basic effect that is known as Stevens effect examines luminance variations and
brightness contrast. Regarding the experiments, it is known that depending on an
increase in luminance level, brightness contrast also increases, and apparently dark
colors appear darker and light colors appear lighter when luminance level is increased.
According to Stevens effect, a power function is cited between perceived brightness and
measured luminance, which is known as Stevens power law in psychophysics. It shows
the estimations of an average relative brightness magnitude as a function of relative
luminance for different adaptation levels (Fairchild, 2005).
As it was mentioned before, to do a color matching between stimuli, some conditions
should be provided equally. If surrounding or background conditions in two settings are
not the same, in manner of luminance levels, a shift of brightness perception named
simultaneous contrast occurs. It can simply be explained as the change in a surface color
appearance caused by an adjacent surface which is brighter or darker than the other
(Michel, 1996). Figure 3.3 illustrates an example of simultaneous contrast. While the top
two small gray square patches are perceived to be the same, the one on the white
background looks darker and the one on the black background looks lighter.
29
Figure 3.3. Simultaneous contrast (Achromatic). (Fairchild, 2005, p. 112)
Color changes in simultaneous contrast follow the opponent theory of vision, which
mentions the cones system as processing according to three opponent channels of red
versus green, blue versus yellow and black versus white (Fairchild,2005). Therefore,
simultaneous contrast can also be seen in chromatic colors and “a red background would
tend to induce a green color shift, a green would induce a red, a blue induces yellow,
and yellow induces blue” (see Figure 3.4) (Johnson and Fairchild, 2005, p. 42).
Figure 3.4. Simultaneous contrast (Chromatic).
30
Lastly, Bartleson- Breneman effect also deals with the variation in luminance level and
the effect of surround on complex stimuli. Bartleson and Breneman observed some
differences in perception of contrast when the luminance level of a stimulus‟ surround is
changed. As the luminance of the surround is increased, perceived contrast also
increased because “when an image is viewed in a dark surround, black colors look
lighter while the light colors remain relatively constant” (Johnson and Fairchild, 2005,
p. 52). However, black colors start to look darker when the luminance is increased and it
causes overall view to appear in higher contrast.
The level of illuminance and luminance are both effective factors in perceived
brightness as well as spatial structure and background of the stimulus. By increasing and
decreasing the level of the light source, or creating different combinations of luminance
levels, the appearance of an image or a stimulus object dramatically changes.
3.1.3.3. Effects on Saturation
Similar to the effects on hue and brightness, luminance level and color of illumination
are also important factors in perceiving the saturation of a stimulus in relation to its
surround. One of the effects which deal with perceived saturation is Hunt effect. To
observe that effect, Hunt used a haploscopic matching, in which the viewer considers
two different stimuli conditions in his two eyes and tries to adjust their color in order to
obtain equal colorimetric purity (Fairchild, 2005). As a result, to equalize the saturation
of a low luminance surrounding with a high luminance one, there is much more
31
colorimetric purity required. Hunt (1952) mentions in his results that “at high levels of
adapting light intensity, increasing the test color intensity caused most colors to become
bluer” (p.49). These results highlight the fact that luminance level is an influencing
factor in perceived saturation, as it is for brightness (Johnson and Fairchild, 2005).
According to that effect, chromatic contrast of the stimulus increases when the
brightness of surround increases.
All of these effects of luminance and illuminance, considering the environmental
constraints of the stimuli are significant factors in perceiving color in the visual world.
Therefore, they are of great importance for this study, and the design of the experimental
set-up takes into account these effects of light and surrounding on color appearance of
spaces, in relation to the appearance of surfaces.
3.2. Color in Depth Perception
Color of the objects has a considerable effect on depth perception in the visual field
(Dresp and Guibal, 2004). In that sense, it is one of the most commonly debated cues,
about which there are critical works (Sundet, 1978). This section is going to cover these
works which concern the cues of depth perception and color attributes which affect the
perception of depth. Color attributes consist of hue, brightness and saturation. Besides
these parameters, the source (light), which makes the color occur in the visible
environment, has also been mentioned in the following sections.
32
3.2.1. Effects of Hue, Brightness and Saturation on Depth Perception
As Sundet (1978) mentions the effect of color on objects‟ apparent distances has long
been known. This situation has mostly been practiced with “highly saturated colors and
with objects lying near each other” (Sundet, 1978, p. 133). One of the earliest and wellknown studies on this subject was conducted by Luckiesh (1918) with the letters of red
„X‟ and blue „E‟ by asking the participants to move the letters back and forth in an
apparatus until they came on to the same plane. He used tungsten lamp to illuminate the
letters and the boxes were equipped with blue and red filters in order to obtain the
colored view. In the study, as the advancing quality of the red, most of the time red „X‟
was moved by the participants further away in order to make it appear on the same plane
with blue „E‟.
This phenomenon has been explained by Sundet (1978) with an optical case, under two
parameters of depth perception, namely monocular and binocular. About the monocular
theory, Sundet (1978) states that short-wave light refracts in the eye‟s optical media
more than long-wave light, and because of this phenomenon, the equidistant sources of
different colors cannot be simultaneously focused on the retina, which is called
chromatic aberration. According to chromatic aberration, a short-wave light source
occurs nearer than a long-wave light source (see Figure 3.5).
33
Figure 3.5. Chromatic aberration. (Sundet, 1987, p.134)
Besides, Sundet (1978) points out that all theories of binocular color-distance have
chromatic aberration in common and this is taken the point of departure. From the
chromatic aberration phenomenon, it is well understood that, wavelength is a stimulus
that affects its perceived depth.
As wavelength of the colors refers to their hue, the studies on hues of colors and their
relation to distance perception are taken into consideration in this part. Before Sundet
(1978) gave the information that colors in themselves have the quality of depth because
of the refraction in the eye, Edwards (1955) mentioned in the conclusion of his
experiment that there is no significant evidence of color itself having the quality of
depth. However, training and association may lead to seeing of some colors as near or
34
far and may provide effective use of color in art for the expression of depth. In
opposition to Edwards (1955), Egusa (1983) explains an effect of hue on perceived
depth as green and blue difference is smaller than the red and green one, in which the
red one appears nearer.
Furthermore, in the first outdoor study, Mount, et. al. (1956) also mention the hue
effects on distance perception. In the experiment, they have compared equal brightness
of coloured and gray papers under sunlight. According to the results, they (1956)
express that each color is judged nearer than gray that has equal brightness, and the hues
appeared closer when viewed against the dark rather than in light. Additionally, Dengler
and Nitschke (1993) mention that when four colors (red, yellow, green and blue) are
seen in front of the black background, long-wavelength colors appear in the front;
however, in front of the white background, the depth perception of colors are reversed.
In that sense, brightness of the background of a stimulus affects depth perception of the
colors as well. However, there is still a gap on the depth perception of different hue
combinations in terms of the stimuli and the background. Besides that, Mount et. al.
(1956) also point out that saturation and brightness contrast are more effective on depth
perception than the difference in distance perception of one hue over the other.
As another parameter of color, saturation is also mentioned in many studies. In general,
as Sundet (1978) remarks, high saturated colors are used in the experiments. According
to Mount et al. (1956), the apparent position of a color is advanced when the saturation
35
of its color is increased in contrast to its background. In this manner, it can be
understood that the saturation difference between the stimulus and the surrounding also
bears importance for depth perception. Besides, Egusa (1983) notes that if the higher
saturated color is red or green, they are judged nearer, but such an effect cannot be seen
with blue color. In a more recent study conducted by Bailey et.al. (2006) with different
coloured three dimensional objects of teapots and backgrounds on the computer screen,
it is pointed out that similar results with high saturated warm or cool colors are obtained
with less saturated colors in apparent distance perception.
Camgöz, Yener and Güvenç (2004) name saturation as the secondary attribute of color
in judgment of „nearness‟, whereas the brightness is the most dominant attribute. The
apparent brightness and brightness contrast are also one of the most commonly studied
cues in depth perception. In Michel‟s (1996) book, the aspect of perceiving brightness is
said to be gamma movement. Gamma movement is explained by Michel (1996) as
follows: as the object brightness is increased, the object “[…] appears to advance toward
the viewer from its initial fixation point […] it returns to its former position” (p. 12) when
brightness is decreased.
The relation of brightness with colored object distance perception was explained as
insistency quality of color by Katz in 1935, which is cited in Payne (1964). He (1964)
describes the insistency of a color as the power of a color to catch the eye and hold it
steadily, and he added that the insistent color appears nearer. Sundet (1978) comments
36
on that statement that the perceived relative distance may be affected by relative
brightness of the colored objects.
In another study considering the brightness effect on depth perception, Taylor and
Sumner (1945) use fluorescent lamps and colored papers (red, yellow, green, blue,
white, black and neutral gray) in different brightness levels. Although the papers are in
different colors, Taylor and Sumner‟s (1945) focus is on the brightness differences. In
the experiment, they observe that the bright colored papers are drawn farther in the
apparatus in order to equalize their apparent distances to each other. Thus, they state that
at a constant distance light colors appear nearer than dark colors. Furthermore, in
another study by Johns and Sumner (1948) which was conducted to verify the study of
Taylor and Sumner (1945), the same result of bright colors appearing nearer than dark
colors at the constant distance is obtained. According to the results, the order of the
colors from the one that appears nearest to the one that appears farthest is red, white,
yellow, green, blue and black. For this experiment, it is noted that the cues which the
subjects use to make the equalization are relative sharpness of the vertical edges and
relative thickness of the colored papers, which are going to be the cues that the
participants will focus on in our experiment as well.
The brightness effect also appears to be one of the contrast differences in adjacent
colours referring to stimuli-surrounding relation. Payne (1964) mentions that if a colour
differs from the background more, it stands farther away from the background. Thus,
37
one of the two colours which is more similar to the background will appear more distant
than the other. In a similar way, Ichihara et. al. (2007) claim that contrast is an
important cue for perceiving the depth of an object. It creates some illusions on the
appearance of colored surfaces in the manner of depth perception (Michel, 1996).
Ichihara et. al. (2007) divide contrast into two as area contrast and texture contrast. They
(2007) define area contrast as “the difference between the average luminance of the
surface area of an object and the average luminance of the background” (p. 686). When
area contrast is low, the object looks far from the observer; similarly, it looks near when
the contrast is high. Grandis (1986) defines simultaneous or reciprocal contrast, which
was particularly explained in the Section 3.1.3.2, as two areas of high contrast in
adjacent positions altering the appearance of both. As Grandis (1986) says a light area
next to a dark area appears lighter than it really is. Thus, this simultaneous contrast has
the effect of darkening the dark color and lightening the light color more. The effect of
two colors on each other makes lighter one to be perceived nearer than they are as an
effect of color kinetics. He explains color kinetics in relation with simultaneous contrast.
He mentions color kinetics as a property which makes color to appear in the front or
back rather than at its real location. Moreover, he continues by saying that this effect
may be because of the degree of luminosity of each color under lighting.
The literature on brightness, darkness and contrast effects of colors has also been
searched under the subject of spaciousness and room size of the space. Taylor and
Sumner (1945) state that rooms done in white, light yellow, light green would appear
38
smaller than they really are. However, Mahnke (1996) claim that light or pale colors
recede and increase the apparent room size whereas dark or saturated colors decrease the
apparent size of the room. Clearwater (1986) mentions that depth perception studies
which are conducted with apparatus are also done by full-scaled room with movable
walls. She (1986) adds that researchers have studied brightness effect alone; hue and
saturation levels of the colors have been controlled in full-scaled studies. She (1986)
claims that “apparently, a lightly colored space appears larger, and there is a recession of
blue that is highly dependent on its saturation” (p. 76). Michel (1996) also mentions that
regardless of its physical size, a bright room is perceived as more spacious.
3.2.2. Effect of Light on Depth Perception
As it is intensively mentioned many times, for the appearance of surface colors,
illumination has a great importance because light makes colors and surfaces visible.
Color and light are the parameters which are specified simultaneously while color is also
involved in light itself. Thus, the surface has the property of absorbing, reflecting and
refracting the light with respect to generating its color. This relation between
illuminance of light and color is mentioned by Yamauchi and Uchikawa (2005) in that
the perceived color of an illuminated surface which is observed from a small window
changes when the intensity of the illumination increases. The color appears opaque and
right on the small window without any depth when the intensity of the illumination is
low, and the color appears brighter and distant as the intensity of the illumination
increases.
39
Coules (1955) has also set an experiment including illuminated opal glass discs with
different intensity levels in order to understand the brightness effect on both monocular
and binocular viewing. He (1955) states that both under monocular and binocular
conditions, brightness influences judgment of distance. He (1955) mentions that in
binocular viewing, the subject who has right eye dominance judges the light stimulus on
his right to be nearer although it is in fact farther. Similarly, it is observed that the
subject with left eye dominance judges that the light stimulus on the left is nearer.
The most basic distance perception experiment with colored light sources has been done
by Pillsbury and Schaefer (1937). In the experiment, they use red neon or blue neon and
argon lights which the participants can view through artificial pupil like slits. The
participants view the different colored lights monocularly and judge their distances.
According to the result, Pillsbury and Schaefer (1937) state that even when they put blue
light farther than the red light, blue light is judged nearer. This is an opposite result
when compared to distance perception of colored surfaces in which the red one is
generally perceived nearer than blue. This effect can be explained by Purkinje shift as
blue light appears brighter than red at low luminance levels; however, in their paper
there is no specific remark about the luminance level. Besides, there is a relation
obtained between the color of stimulus and the intensity of its surrounding in the manner
of depth perception by Dengler and Nitschke (1993). According to their (1993) studies,
the short-wavelength colors are seen farther than long-wavelength colors when the
40
intensity levels of these stimuli are greater than the intensity level of stimulus
surrounding. This effect is reversed, when the lighting conditions are also reversed.
In recent years, some other experiments by Huang (2007) have been done on colored
lights and depth matching tasks. In his experiment, he uses colored lights and colored
surfaces in a box-like apparatus and he asks the participants to equalize the distances of
the colored chips. The experiment has been done both with monocular and binocular
viewing. According to the results, he mentions that the perceived distance difference in
binocular viewing is significantly less than the monocular viewing because of the
convergence and disparity manipulations on depth. Besides, he has found an effect of
green light, under which there are more distance differences perceived than white and
yellow light. Moreover, perceived distance under white light is less than blue light. With
reference to these results, he determines a significant effect of colored light on distance
perception. Upon another study, there were no significant differences obtained between
blue and green light conditions, neither with yellow, red and white light conditions
(Huang, 2009). However, he declares that since the five colored lights are used in
different hues and intensities, it is not specifically known whether the results are due to
hue or intensity variations. Referring to that, this study focuses on the hue attribute of
color and its relation with its surrounding, in this case the background, in order to
understand if hue difference has an effect on depth perception.
41
4. THE EXPERIMENT
4.1. Aim of the Study
The aim of the study is to understand the relationship of color with distance perception
in interior spaces. To understand this relationship, different object and background color
combinations are tested.
4.1.1. Research Questions
The research questions of study are as follows:
1. Are there any effects of colored light on distance perception in interior spaces?
2. Does background color affect depth perception of different colored objects?
4.1.2. Hypotheses
The hypotheses of the study are as follows:
1. There are depth perception differences between different backgrounds with
different hues.
2. There are depth perception differences between different hue combinations of
background and object.
3. There are depth perception differences between different color temperatures of
white lit background according to the hue of the object in front of it.
42
4.2. Method of the Study
The method of the study is explained under the sections of sample group, experiment
room and stimuli, and procedure. The information about experiment considering
participants, stimuli and how the experiment is conducted can be followed in detail in
the next three sections.
4.2.1. Sample Group
To the first phase of the study, 35 students who were having their internships in Philips
Research Eindhoven, Netherlands participated. 4 of them were female and 31 of them
were male. They had engineering or industrial design backgrounds with the ages
between 22-29. They had little to no knowledge of color and depth cues, in order to
avoid possible biases and the influence of personal experience. Additionally, the
experiment was conducted in English due to having participants from different
nationalities who were capable of speaking and understanding English. To the second
phase, 21 students who had the most consistent results according to their responses to
the questions from the first phase participated.
4.2.2. Experiment Room and Stimuli
The experiment was conducted in the Shoplab of Holst Center, at High Tech Campus,
Eindhoven. The room had no exterior windows, however, had shop windows which
43
looked out on an inside hall. Those windows were covered with curtains in order not to
have any other light source inside the experiment room. The measures of the room were
11m x 6m and ceiling height was 2.6m. As the lab was designed as a shop, there were
some shelves and cloth hangers; however, all the exhibited clothes were removed and all
the side walls remained white during the experiment. Besides, stable furniture which
was in the visual scene was covered with black curtains. The floor of the room was
covered with gray carpet.
The room had eleven different types of lamps with several types of installations. The
main installations in the room were LED and halogen spots, fluorescent and LED
wallwashers and general lighting devices. For the experiment, LED wallwashers of
ColorKinetics Colorblaze (Philips) were used. Three lights of nearly 1.80 meters which
were containing 12 LED groups were installed in the ceiling and three other lights were
installed at the bottom of the wall. Every LED group had a small colorful finger-like
effect on the wall. In order to drive the lights, the LightMan program was used with
DMX controller. The lights could be driven with given intensity levels of their white or
RGB channels. The arrangements on light levels and color were done with dimming in
those RGB channels. The main reason for choosing this room for the experiment was to
have sufficient viewing distance from the stimuli and to have more uniform lighting
conditions on the stimuli background.
44
The stimuli consisted of the background which was lit with the wallwashers and two
objects were situated in front of it. During the experiment six different colors of
wallwashers were used in the background: orange, blue, red, green, warm white (3000K)
and cool white (6500K). These colors were chosen with reference to the previous studies
in literature (Mount et. al, 1956; Pillsbury and Schaefer, 1937; Dresp and Guibal, 2004;
Huang, 2009) and also to have equal numbers of cool and warm colors. In that sense,
orange and red were the long-wavelength and warm colors, whereas blue and green
were the short-middle-wavelength and cool colors. Besides, white light was taken as the
control light color, where also if color temperature made any difference on depth
perception was tested. In order to understand the hue effect, their lightness and chroma
were matched as close as possible to each other. The matching of colors was done with
3000K white point as it also represented the eye adaptation level of color temperature in
the experiment. The LCH (Lightness, Chroma and Hue) of the colors were measured
with Photo Research Spectra Duo PR 680 and Macro Spectar MS-75 lens. The LCH
values of the color can be seen in Table 4.1.
Table 4.1. The LCH values of six background colors.
Color of the
Background
Lightness
Chroma
Hue
Color of the
Background
Lightness
Chroma
Hue
Warm white
58.69
3.7
O
Red
59.54
54.79
10.13
Cool white
58.37
77.92
274
Blue
55.64
55.98
244.39
Orange
57.89
56.89
48.13
Green
58.68
54.76
168.34
45
During the experiment, 2 sets of background were shown to the participants with the
same colored objects in both of the sets; one of the background set was cool white and
the second one was a two colored pair of the six light colors which were previously
mentioned (see Figures 4.1 and 4.2). In front of the background, 2 identical objects in
the dimensions of 45cm x 45 cm were placed. In the experiment, three different colors
of objects were used in orange, blue and gray (see Table 4.2). Again referring to the
literature (Pillsbury and Schaefer, 1937; Sundet, 1978; Dresp and Guibal, 2004), red and
blue were chosen as object colors; however, according to a more recent study conducted
by Seuntiens and Vogels (2008) orange instead of red was evaluated as creating a cosier
atmosphere, so it was more preferable by individuals for use in interior spaces. Besides,
cases with gray objects were also tested in order to have a control group of colored
objects.
Figure 4.1. The stimuli with cool white lit background and gray objects.
46
Figure 4.2. The stimuli with one color combination (red-blue) of background light and
gray object.
Table 4.2. The LCH and NCS values of three object colors.
Color of the
Lightness
Chroma
Hue
NCS value
Object
Orange
61
50
47
2050 Y60R
Blue
61
47
236
1060 B
Gray
59
0
0
5000 N
Those object colors were chosen from NCS according to their luminance and saturation
values. The NCS codes of the colors were as follows: orange (2050- Y60R), blue (1060B), gray (5000N). The colors of objects were also arranged as close as possible in their
47
lightness and chroma to each other and to the six background colors in order to
eliminate the effects of other color attributes and to find out specifically the effect of hue
difference on distance perception. In the set-up, the two identical objects were also
illuminated with spots which were fixated on top of the objects and could be moved in
the same direction as the objects. They were two identical Philips Diamondline Halogen
spots with 50 W, 12 V, 3000 K color temperature and 24º of angle to minimize shadows
on the background.
The stimulus was seen from 10 m viewing distance with a chinrest by the participant in
order to stabilize head movements (see Figure 4.3). 10 m viewing distance was provided
for the experiment in order to avoid the undesired effects of depth cues which have
already been displayed in Figure 2.1. Also, a black cross between the two objects was
arranged for participants to focus their eye on to concentrate directly onto the colors but
not to the size or shape of the objects while the distances of the objects were being
changed by the experimenter. The participants were informed before the experiment
about where to focus and why.
48
Figure 4.3. Experiment room.
4.2.3. Procedure
At the beginning of the experiment, each participant took Ishihara‟s color blindness test
and the visual acuity test. The ones who had vision deficiencies were asked to take the
test with their correction equipments. After that, different types of experimenting
techniques were tried in order to find the right way to measure the depth perception
differences of the colors. According to that, some pilot tests were conducted and a
forced choice paired comparison test appeared to be the main method to find out if
colors and different color combinations have any effect on distance perception.
49
4.2.3.1. Pilot Studies
Before continuing with the forced choice method for the experiment, there were
different designs of method tested as pilot studies. At first, a tuning method starting
from equal distances of two objects was conducted. In the method, the left object stayed
stable and the right object was moved to the front or the back according to the
participants‟ instructions. However, in this method no difference was perceived by the
participants. As the second method, a two-way tuning starting from different positions
of two objects was conducted. In this method, while the right object stayed stable, the
left object was moved from the front to the back and from the back to the front
according to the participants‟ instructions in order to equalize the distances of the two
objects from the point of view of the participants. After the participation of two subjects,
varied results were obtained depending on the subjects, and this turned out to be a hard
experiment for the participants to follow and respond.
Due to the varying results of each participant, it was decided that the baselines for each
participant should be measured. In baseline measurements, cool white background with
two objects in the same color were judged by the participants. Hence, no differences
between objects and the background of these objects; in other words no perceived
differences between them were expected. However, each participant perceived varying
differences between the distances of two objects; for this reason, a baseline
measurement was necessary for each participant in order to specify their zero point.
Consequently, a two-way tuning method with baseline measurement was conducted. In
50
this method, random repetitions of front-back and back-front of the objects displayed
once again and large variations between baselines of different participants were
obtained. Since the two-way tuning method was hard for participants to manage, a
paired comparison test was found suitable to be applied with baseline measurements.
Due to the statistical method that was going to be used (Monte Carlo method with
psychometric curves), the paired comparison test was done in forced choice method. In
forced choice method, “[…] the influence of varying observer criteria on the results” can
be eliminated (Fairchild, 2005, p. 44).
4.2.3.2. Forced Choice Paired Comparison Test
The experiment is completed in two phases in which the first one leads to the second
phase in order to have more reliable and valid data to consider the hue differences and
background-object combinations.
4.2.3.2.1. First Phase
At the beginning, thirty five combinations of stimulus with colored lit background pairs
and two same colored objects which were created with 6 light colors and 3 object colors
were judged by thirty five participants. Each participant evaluated 2 cases; one with cool
white background and the second one with one of the combinations shown in Table 4.3.
51
Table 4.3. 35 combinations of object and background colors.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Object color
orange object
orange object
orange object
orange object
orange object
orange object
orange object
orange object
orange object
orange object
blue object
blue object
blue object
blue object
blue object
blue object
blue object
blue object
blue object
blue object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
Colored Background Pair
warm white light
blue light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
blue light
cool white light
green light
cool white light
red light
blue light
green light
blue light
red light
red light
green light
warm white light
orange light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
orange light
cool white light
green light
cool white light
red light
orange light
green light
orange light
red light
red light
green light
warm white light
blue light
warm white light
orange light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
blue light
cool white light
orange light
cool white light
green light
cool white light
red light
orange light
blue light
orange light
green light
orange light
red light
blue light
green light
blue light
red light
red light
green light
52
As it was already learned from the pilot studies that even the baselines of the
participants vary the one with cool white background was taken as the baseline for each
participant to compare the perceived distance difference between the colored pairs. For
each participant, one of the three colored objects (orange, blue or gray) was presented in
front of the lit backgrounds. For two cases of background color, the object colors were
kept constant for each participant. Thus, for each participant only the background color
changed in order to evaluate the absolute distance and understand if color changes on a
wall will make any difference on distance perception. In the color combinations, same
colors both on the object and in the background were never used (orange object sets did
not include orange light as a background and blue object sets did not include blue light
as a background).
During the experiment, the left object stood stable; however, the right object moved
back and forth according to the previously defined distances, and participants were
asked to compare the distances of two objects according to the point where they were
standing and tell which object (right or left) they perceived in the front. Seven points
with 10 cm differences were defined to place the left object. The six points were 30 cm,
20 cm and 10 cm in front of the right object and 30 cm, 20 cm and 10 cm back of the
right object, and the seventh point was 0 cm where the two objects were at an equal
distance to the viewer. Each point was presented 10 times randomly during the
experiment, which made 70 points for each background. As each participant evaluated
two backgrounds, 140 points in total were judged by one participant (see Appendix A
53
for an example of data recording). In order to hide where the object was moved by the
experimenter, participants were asked to close their eyes while the place of the left
object was being altered.
In addition, the experiment was conducted monocularly to avoid the effects of binocular
cues and to make sure that the obtained distance differences were derived because of
color only. The participants took the dominant eye test and they took the experiment
with their dominant eye. In addition, depending on the participants‟ speed of evaluating,
the experiment took 20-35 minutes.
4.2.3.2.2. Second Phase
For the second phase of the experiment, 21 participants who were consistent with their
answers in the first phase were chosen. However, two of these participants had already
left the company, so the experiments were conducted with 19 of them. This phase of the
experiment was for increasing the number of participants for the background colored
pairs. However, since the number of cases that had been planned to be tested was
excessive to be managed with more participants, and the experiments for each
participant took more than 20 minutes, the cases of color combinations were narrowed.
In order to test different hue effects on depth perception, each hue was displayed with
cool white as a pair at the background. As a result, the pairs for background were chosen
as cool white-orange, cool white-blue, cool white-green, cool white-red and warm
white-cool white. Besides, according to the obtained results from the previous phase,
54
there were some similarities between red, green and orange, blue colors, in order to
compare them directly with each other, red-green and orange-blue pairs were also tested
in the second phase. All of those seven background pairs were displayed with the same
three colored objects (orange, blue and gray) which had already been used in the first
phase. Therefore, in total 17 combinations with three object colors and seven
background lit pairs were evaluated (see Table 4.4.). The method was kept the same as
that in the first phase.
Table 4.4. Color combinations evaluated in the second phase.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Object color
orange object
orange object
orange object
orange object
orange object
blue object
blue object
blue object
blue object
blue object
gray object
gray object
gray object
gray object
gray object
gray object
gray object
Colored Background Pair
warm white light cool white light
cool white light
blue light
cool white light
green light
cool white light
red light
red light
green light
warm white light cool white light
cool white light
orange light
cool white light
green light
cool white light
red light
red light
green light
warm white light cool white light
cool white light
blue light
cool white light
orange light
cool white light
green light
cool white light
red light
red light
green light
orange light
blue light
If the participants took the previous experiment with the gray object, then they again
evaluated the gray object in the second phase. By means of this, since we already had
their baselines with the cool white background in the first phase, the second phase was
55
directly conducted with the colored pairs at the background. At the end, each color
combination was evaluated by three participants.
4.3. Findings
For the experiment, Monte Carlo by resampling the psychometric curves with
bootstrapping and ANOVA were used as the statistical methods. In the experiment
many different methods were conducted and forced choice pair comparison test was
found to be the most suitable one. According to the forced choice paired comparison
test, the responses of the participants indicating whether the right or left object is
perceived nearer were taken as the data for psychometric curves. Due to this data (the
responses of 10 times repeating 7 different distance points), either 0 (right object
perceived nearer) or 1 (right object perceived farther) values for curve ranges were
obtained on x-axis to the psychometric curves for both the baseline and the background
pairs for each participant for each color combination. In order to create a model and to
do a proper statistical analysis, the fitted curves for each color combination for a single
participant were resampled 1000 times using the bootstrapping technique to obtain
confidence intervals and more accurate median lines with more valid results. According
to the confidence intervals, median curves of both the baseline and background pair
were obtained (see Appendix B and C). After that, the difference between two median
curves (baseline and background pair curves) from the confidence intervals of 0.5 point
threshold was calculated, and with Monte Carlo method the significances of the color
differences for each participant was estimated. After that, in order to check the overall
56
results of the participants, the differences calculated from 0.5 point thresholds for each
participant were used as dependent variable in ANOVA test (see Appendix D).
ANOVA was run on the complete set of data, with the difference between medians of
baseline and background pairs of each participant as the dependent variable, and object
color (orange, blue, gray) and background pair (cool white-blue, cool white-green, cool
white-red, cool white-orange, warm white-cool white, red-green, orange-blue) as the
independent variables. Results showed that different object colors significantly affected
perception of distance, F (2,34)= 13.83, p< 0.001. Hochberg‟s GT2 test revealed that
there were different depth perceptions occurring between orange and the other two
colors (blue and gray) (see Appendix D). Besides, the mentioned results from ANOVA
and Hochberg‟s GT2 tests, there were also obtained p-values from Monte Carlo tests for
psychometric curves. All the p-values that are going to be mentioned in this chapter for
psychometric curves are the results of Monte Carlo test. According to that, psychometric
curves confirmed that there was a distance difference between object colors, especially
with cool white-green background pair. According to all three participants who
evaluated cool white-green background pair with orange and blue objects, there were no
distance differences; however, when the same background pair with gray objects was
judged, all three participants perceived differences (p=0.008, p= 0.008, p= 0.001) (see
Figure 4.5).
Examine all the psychometric
curves according to;
57
Gray object
Cool white
– Green
background
Difference:
15.14 cm
Gray object
Cool white
– Green
background
Difference:
18.76 cm
Gray object
Cool white
– Green
background
Difference:
18.56 cm
Figure 4.5 Psychometric curves for three participants which are represented one by one
with baseline and background pair measurements.
58
From the psychometric curves, it can be understood that there is a tendency to perceive
the gray object nearer in front of the green background than the cool white background.
If cool white-blue background pair was discussed according to the object colors in front
of it, then all three participants perceived distance differences with orange objects (p=
0.003, p= 0.044, p= 0.042) (see Figure 4.6).
59
Orange
object
Cool white –
Blue
background
Difference: 17.68 cm
Orange
object
Cool white –
Blue
background
Difference: 7.36 cm
Orange
object
Cool white –
Blue
background
Difference: 8.85 cm
Figure 4.6. Psychometric curves for three participants which are represented one by one
with baseline and background pair measurements.
60
According to the psychometric curves, orange object appeared nearer with
approximately 12 cm difference in front of cool white background than blue. Contrarily,
just one of the participants perceived distance difference between cool white and blue
background colors when they were displayed with the gray object, and according to that
participant the gray object appeared nearer with 10 cm difference in front of blue instead
of cool white (p= 0.005) (see Figure 4.7).
Gray object
Cool white
– Blue
background
Difference:
10 cm
Figure 4.7. Psychometric curve for one participant with baseline and background pair
measurements.
Additionally, with red-green background for all three object colors, there was one result
which reveals a distance difference for each object from three participants according to
psychometric curves. For blue (p= 0.003) and gray (p= 0.001) objects, the objects in
front of green background reflected a tendency to be perceived nearer than the one in
61
front of red background. Besides, the difference between colors was 10 cm with blue
object, and it doubled with the gray object. On the contrary, for the orange object, the
one in front of the red background had the tendency to be perceived nearer than that in
front of the green background with a difference of 10 cm (p= 0.022). Furthermore, when
cool white-orange background was considered, there were no differences obtained for
blue object except for just one participant for the gray object (p= 0.020) where the
object in front of cool white background was perceived 10 cm nearer than it was in the
orange background (see Appendix C).
Moreover, in order to understand if color temperature makes any difference in depth
perception depending on the object color in front of it, warm white-cool white
background pair was evaluated for three object hues. According to the psychometric
curves, depth perception difference between warm white and cool white background can
be mentioned for orange and blue objects; however, there was no distance difference for
the gray object. According to Monte Carlo tests, p-values for the orange object from one
participant (p< 0.001) and blue object from two participants (p= 0.042, p= 0.003)
denoted that the blue object had a tendency to be perceived nearer in front of warm
white background, where the orange object had a tendency to be perceived nearer in
front of cool white background. The perceived difference for warm white and cool white
background was 15 cm for the orange object and approximately 10 cm for the blue
object (see Figure 4.8).
62
Orange
object
Warm
white –
Cool white
background
Difference:
-15.48 cm
Blue object
Warm
white –
Cool white
background
Difference:
8.61 cm
Blue object
Warm
white –
Cool white
background
Difference:
12.27 cm
Figure 4.8. Psychometric curves for three participants which are represented one by one
with baseline and background pair measurements.
63
Additionally, the results of ANOVA showed that there was a significant difference
between background hue pairs, F (6, 34) = 2.433, p= 0.046 and according to the results,
there were no significant interaction effects of object color and background color pairs.
However, Hochberg‟s GT2 test revealed that there was a difference between cool whiteblue and orange-blue pairs. Besides, there were some differences between background
hue pairs, which can be mentioned qualitatively with reference to Monte Carlo tests of
the psychometric curves. The interaction effects of colors with background lit pairs can
be seen in Appendix D.
If background sets with the orange object are considered, the effect of cool white-red
background pair was accurate for just one participant (p= 0.015). Also, according to the
difference, the orange object in front of a red background was perceived nearer than it
was in cool white background. Similarly, there were no distance differences observed
for the cool white-green background pair. Although, green didn‟t show any difference
when displayed with cool white, there was an effect of it when displayed as red-green
pair. For one of the participants, orange object in front of the red background had the
tendency to be perceived nearer than it was in front of the green background with 10 cm
difference (p= 0.022) (see Appendix C and E).
In the sets of blue object, there were no distance differences obtained with the cool
white-green and cool white-orange background pairs. Two participants perceived
distance difference between cool white and red backgrounds (p= 0.026). According to
64
the psychometric curves, the blue object in front of the red background had the tendency
to be perceived nearer than it was in front of the cool white background with
approximately 15 cm difference. Besides, one participant perceived distance difference
between the red and green backgrounds (p= 0.003) in which the blue object in front of
the green background was perceived 10 cm nearer than it was in the red background (see
Appendix C and E).
With the sets of gray object, similar effects of cool white-blue, cool white-green, cool
white-red and cool white-orange pairs on distance perception were observed in the
psychometric curves. In all of those cases, if there was a difference between the median
curves of the participants, these differences indicated that the object in front of the
colored backgrounds had a tendency to be perceived nearer than it was in front of the
cool white background (see Appendix C, and E for the plots, their p-values and
perceived differences between the colored background pairs). For cool white-green pair,
this difference was accurate for all three participants and the difference perceived
between cool white and green hues was approximately 18 cm (p= 0.008, p= 0.008, p<
0.001). This pair had the biggest difference and cool white-red pair follows cool whitegreen pair with the approximate distance difference of 15 cm, but in this case, the results
of two participants were accurate (p= 0.001, p= 0.005) instead of three. Besides these,
for both cool white-blue (p= 0.005) and cool white-orange (p= 0.020) pairs, there was
one accurate result obtained for each background pair from three participants. According
to these results, both hues indicated approximately 10 cm difference from cool white
65
background. In this manner, distance differences with green and red backgrounds were
more accurate than the distance differences with blue and orange backgrounds compared
with cool white due to higher distance differences.
In addition, however, there were similar results for the pairs of cool white-blue and cool
white-orange. When blue and orange hues were displayed together as a pair, distance
difference was obtained for all three participants (p= 0.026, p= 0.004, p= 0.008).
According to these results, the gray object in front of the blue background had a
tendency to be perceived nearer than it was in the orange background with the
approximate difference of 13 cm. On the other hand, when red and green hues were
displayed as a pair, the distance difference was perceived by one participant (p= 0.001)
instead of three or two as it was in cool white-green and cool white-red pairs, and the
perceived difference was nearly the same in all three background conditions. For the
summary of results according to the colored background pairs see Table 4.5.
66
Table 4.5. Presentation of which colored object was perceived nearer in front of which
colored background and how many participant perceived difference for each background
pair.
Colored
Background Pair
Cool white-blue
Orange Object
Perceived
nearer
Particip
ant nb.
Cool
white
3
Perceived
nearer
0
Cool white-green
Cool white-red
Blue Object
Red
1
Red
Cool whiteorange
Warm white-cool
white
Red-green
Particip
ant nb.
Perceived
nearer
Particip
ant nb.
Blue
1
0
Green
3
2
Red
2
0
Orange
1
Warm
white
1
Cool
white
2
Red
1
Green
2
Orange-blue
67
Gray Object
0
Green
1
Blue
3
5. DISCUSSION
In this study, the effects of different colors and different color combinations on depth
perception in interior spaces were studied. It was hypothesized that there are different
depth perceptions according to the background hue and its combination with objects
which has different hues. Another hypothesis was that there are differences in depth
perception depending on the color temperature of background lit and object hue in front
of it. The differences in the perception were analyzed depending on object color and
background color.
The results showed some similarities and differences with the literature. When object
colors were analyzed, blue and gray colored objects were found to have similar
tendencies in differences, where the orange object generally showed opposite results,
which verifies the hypothesis of the study. Blue and gray colors are cooler than the
orange object and they were generally perceived farther than the orange one, which
shows a similarity to the study carried out by Bailey et. al. (2006). According to their
(2006) study, warmer colored objects appeared closer than cooler ones. Besides that,
mainly there were bigger differences observed with the gray object than the blue or
orange object. Mount et. al. (1956) mentioned that “each color was seen in front of its
nearest matching gray” (p.210). In this study, it is revealed that blue and orange were
68
generally perceived nearer than gray, which had the nearest brightness matching with
the other two colors.
Another similarity with the literature can be mentioned about red and blue
combinations. According to the literature, due to chromatic aberration “red and blue
showed especially striking differences” (Pillsbury and Schaffer, 1937, p. 126). In this
study, when blue object sets were analyzed, the biggest difference was obtained with
cool white-red background pair. Besides, for the orange object, the biggest difference
was also perceived with cool white-blue background pair.
Contrary to the information in the literature which claims that short-wavelength colors
appear nearer than long-wavelength colors, the results of this study doesn‟t follow the
same order. Instead of warm and cool colors theory, it is possible to mention the effect
of opponent-colors theory (Fairchild, 2005). According to the theory, there is a
fundamental phenomenon about red-green and yellow-blue pairs in terms of color
receptors in the brain. Cone signals allow construction of red-green (L-M+S channels)
and yellow-blue (L+M+S channels) opponent signals (Fairchild, 2005). When gray
object sets were analyzed in order to find out about background color effect, cool whitered and cool white-green backgrounds had similar differences in the same direction, as
cool white-blue and cool white-orange background pairs had similar effect. With cool
white-blue and cool white-orange pairs the difference was half as much as it was in cool
white-red and cool white-green pairs. Moreover, for all of the background pairs, the
69
object in front of the colored backgrounds was perceived nearer than it was in cool
white background. Furthermore, when red-green background pair was evaluated, it,
however, changed according to the participant, so no big differences were obtained.
Besides, when orange-blue background pair was evaluated there was a significant
difference. In that case, it is possible to say that different background combinations also
have an effect on depth perception. Additionally, for background color combinations,
there was no effect of color temperature on depth perception when it was judged with
gray object; however, depending on object color, it showed differences in different
directions.
As a limitation of the study, due to the baseline and estimation of the distance variations
between participants, a method which had specific measuring points and repetitions
were applied. Therefore, each participant took a longer experimental period than
expected. Hence, three participants for each color combination could be taken to the
experiment and because of the variations between them it was not suitable to evaluate all
of the data obtained from all of the participants regardless of the confidence intervals.
Consequently, to explore the effects of color on depth perception, the results obtained
from the psychometric curves of participants were also interpreted one by one. In future
studies, to standardize the baseline factor and to provide the perceived distance
difference, a starting point for the previously specified 7 points can be determined
according to the baselines of each participant instead of keeping it stable for each
participant. In other words, if a participant has a deviation of 10 cm, the starting point
70
can be taken as 10 cm instead of 0 cm and the distances can be specified as 20, 30 and
40 instead of 10, 20 and 30.
71
6. CONCLUSION
The effects of color and its combination with colors of the background light on depth
perception in interior spaces were investigated in an experiment which had two parts
depending on the participants‟ contribution to the test. The results of the statistical study
showed significant effects of color and colored light on depth perception in terms of
different baselines and distance perception of participants.
As indicated in the literature review, different cues of depth have been studied including
object color and light color effects with small colored chips and mock-up designs
(Mount et. al., 1956; Bailey et. al., 2006; Ichihara et. al., 2007; Huang, 2007). Besides,
all of them have generally examined brightness and saturation attributes of color and
their influence on depth perception. There are no studies exploring hue effect on depth
perception in 1/1 scaled interior spaces with the combination of object color and light
color. The results of this research are important to fill the gap in the literature about
color and colored light effects in interior spaces. It is observed that the effects of color
and colored light on depth perception shows variations between participants.
The results of this study can be useful for interior architects, lighting and stage designers
who need to create different depth perceptions in a space with object and background
relations. In order to intentionally create the required atmosphere in the space, it is
72
important for a designer to know the effect of color and light in a space. According to
the study, the differences between hues are smaller than the variations in the baselines of
the participants; because of that, these differences may not be applicable in the design
field as it was expected. However, it is understood that as hue is found to have a small
effect on depth perception with varying differences between participants, it is a less
effective factor for depth perception than brightness effects which were obtained in
other studies in the literature (Taylor and Sumner, 1945; Johns and Sumner, 1948;
Mount et. al., 1956). Thus, designers may focus on brightness or saturation to obtain the
desired effect of depth illusions more than hue.
Apart from the benefits of this study for the design field, the results can also be
contributive to color science and human psychology studies concerning perception.
Moreover, according to the experiences obtained from the longstanding method trials
and implementations, it can also play an important role on how to generate the methods
of experiments dealing with perception.
In future studies, if binocular viewing makes any difference on depth perception of
colors and color lights in order to find out more practical usages and applications can be
investigated. Besides, how colors and color combinations affect the room size can be
looked into by making a contribution to this study in order to understand if the results
obtained from depth perception tests are mostly influenced by the background or object
73
colors. A more detailed research can be done in order to understand the reasons why the
perception of participants showed so much variation with each other in the study.
74
REFERENCES
Agoston, G. A. (1987). Color Theory and Its Application in Art and Design. Berlin:
Springer- Verlag.
Anstis, S. (2002). The Purkinje rod-cone shift as a function of luminance and retinal
eccentricity. Vision Research, 42, 2485-2491.
Bailey, R., Grimm, C. & Davoli, C. (2006). The real effect of warm-cool colors.
International Conference on Computer Graphics and Interactive Techniques.
Boston: Massachusetts.
Boff, K. R., Kaufman, L. & Thomas, J. P. (1986). Handbook of Perception and Human
Performance. New York: John Wiley and Sons.
Camgöz, N., Yener, C. & Güvenç, D. (2004). Effects of hue, saturation, and brightness:
Part2: Attention. Color Research and Application, 29, 20-28.
CIE. (1988). CIE publication No. 17.4: International lighting vocabulary.
Vienna: Central Bureau of Commission Internationale de l'Eclerage.
Clearwater, Y. (1986). Space Station Habitability: Interior Color Team- an
Introduction. Moffit Field, California: Nasa.
Cook, N. D., Yutsudo, A., Fujimoto, N. & Murata, M. (2008). Factors contributing to
depth perception: Behavioral studies in the reverse perspective illusion. Spatial
Vision, 21, 397-405.
Coren, S., Ward, L. M. & Enns, J. T. (1994). Sensation and Perception (4th edition).
Forth Worth: Harcourt Brace College Publisher.
Coules, J. (1955). Effect of photometric brightness on judgments of distance. Journal of
Experimental Psychology, 50, 19-25.
Cutting, J. E. & Vishton, P. M. (1995). Perceiving layout and knowing distances: The
integration, relative potency, and contextual use of different information about
depth. In Epstein, W. & Rogers S. (Eds.). Handbook of Perception and
Cognition, Vol.5, Perception of Space and Motion. (pp. 69-117). Cambridge:
Academic Press.
Dengler, M. & Nitschke, W. (1993). Color Stereopsis: A model for depth reversals
75
based on border contrast. Perception and Psychophysics, 53, 150-156.
Dresp, B., Durand, S. & Grossberg, S. (2002). Depth perception from pairs of
overlapping cues in pictorial displays. Spatial Vision, 15, 255-276.
Dresp, B. & Guibal, C. R. (2004). Interaction of color and geometric cues in depth
perception: When does “red” mean “near”? Psychological Research, 69, 30-40.
Edwards, A. S. (1955). Effect of color on visual depth perception. The Journal of
General Psychology, 52, 331-333.
Egusa, H. (1983). Effects of brightness, hue and saturation on perceived depth between
adjacent regions in the visual field. Perception, 12, 167-175.
Fairchild, M. D. (2005). Color Appearance Models. John Wiley and Sons: England.
Gombos, K & Schanda, J. (2006). Interrelationship between size and brightness
dimensions of appearance. CIE Expert Symposium on Visual Appearance, Paris,
France.
Grandis, L. D. (1986). Theory and Use of Color. New York: Prentice Hall.
Grossberg, S. (1994). 3D vision and figure-ground separation by visual cortex.
Perception and Psychophysics, 55, 48-120.
Huang, K. C. (2007). Effects of colored light, color of comparison stimulus, and
illumination on error in perceived depth with binocular and monocular viewing.
Perceptual and Motor Skills, 104, 1205-1216.
Huang, K. C. (2009). Effects of colored lights, spacing between stimuli, and viewing
distance on error in a depth- matching task. Perceptual and Motor Skills, 108,
636-642.
Hunt, R. W. G. (1952). Light and Dark Adaptation and the Perception of Color. Journal
of The Optical Society of America, 42, 190-199.
Ichihara, S., Kitagawa, N. & Akutsu, H. (2007). Contrast and depth perception: Effects
of texture contrast and area contrast. Perception, 36, 686-695.
Ittelson, W. H. (1960). Visual Space Perception. New York: Splinger Publishing
Company.
Johnson, G. M., & Fairchild M. D. (2005). CRC: Chapter on visual psychophysics and
76
Color appearance. Retrieved July 23, 2007, from page 3 at
www.cis.rit.edu/fairchild/PDFs/PAP13.pdf.
Johns, E.H. & Sumner, F.C. (1948). Relation of the brightness differences of colors to
their apparent distances. Journal of Psychology, 26, 25-29.
Katz, D. (1935). The World of Colour. London: Kagen Paul.
Kawabe, T. & Miura, K. (2006). Recovering depth-order from orientation-defined
junctions. Psychological Research, 70, 375-383.
Luckiesh, M. (1918). On “retiring” and “advancing” colors. American Journal of
Psychology, 29, 182-186.
Mahnke, F. H. (1996). Color, Environment and Human Response. New York: Van
Nostrand Reinhold.
Matlin, M. W. & Foley, H. J. (1997). Sensation and Perception (4th edition). Boston:
Allyn and Bacon.
Michel, L. (1996). Light: The Shape of Space- Designing with Space and Light. New
York: Van Nostrand Reinhold.
Mount, G. E., Case, H. W., Sanderson, J. W. & Brenner, R. (1956). Distance judgment
of colored objects. The Journal of General Psychology, 55, 207-214.
Padgham, C. A. & Saunders, J. E. (1975). The Perception of Light and Colour. New
York: Academic Press
Palmer, S. E. & Brooks, J. L. (2008). Edge-region grouping in figure –ground
organization and depth perception. Journal of Experimental Psychology, 34,
1353-1371.
Payne, M. C. (1964). Color as an independent variable in perceptual research.
Psychological Bulletin, 61, 199-208.
Pillsbury, W. B. & Schaefer, B.R. (1937). A note on advancing-retreating colors.
American Journal of Psychology, 49, 126-130.
Pridmore, R. W. (2007). Effect of purity on hue (Abney Effect) in various conditions.
Color Research and Application, 32, 25-39.
Taylor, I. L. & Sumner, F. C. (1945). Actual brightness and distance of individual colors
when their apparent distance is held constant. Journal of Psychology, 19, 79-85.
77
Sekular, R. & Blake, R. (1994). Perception (3rd edition). New York: Mc Graw- Hill.
Seuntiens, P. J. H. & Vogels, I.M. L. C. (2008). Atmosphere Creation: The Relation
between Atmosphere and Light Characteristics. Eindhoven: Philips Research.
Steven, S. S. (1988). Steven’s Handbook of Experimental Psychology. New York: John
Wiley and Sons.
Sundet, J. M. (1978). Effects of colour on perceived depth: Review of experiments and
evaluation of theories. Scandinavian Journal of Psychology, 19, 133-143.
Valberg, A. (2005). Light Vision Color. England: John Wiley and Sons.
Williams M. M. & Tresilian, J. R. (1999). Some recent studies on the extraretinal
contribution to distance perception. Perception, 28, 167-181.
Wyburn, G. M. (1964). Human Senses and Perception. Canada: University on Toronto
Press.
Yamauchi, Y. & Uchikawa, K. (2005). Depth information affects judgment of the
surface color mode appearance. Journal of Vision, 5, 515-524.
Zukauskas A., Shur M. S., & Gaska R. (2002). Introduction to Solid State Lighting.
England: John Wiley and Sons.
APPENDICES
78
APPENDIX A
79
Table A.1 Sample data list for one participant from phase 2.
Participant 1/ Right Eye/ age: 25
cw
10
L
0
30
L
-30
10
L
-10
10
L
-30
30
L
30
-20
R
30
-30
R
-20
-10
L
-20
-30
L
-10
-10
L
30
-30
R
20
0
L
10
20
L
20
30
L
-10
-20
R
-30
0
L
20
-10
L
-10
-10
L
0
10
L
10
-10
L
-10
-30
L
30
20
R
-20
-30
R
-20
-20
L
0
-20
L
10
-20
L
20
0
L
30
30
L
0
20
L
10
0
L
20
10
L
10
0
L
-30
20
L
-20
20
L
0
30
L
-30
cw-bl
L
R
R
R
L
L
L
L
L
L
L
L
L
L
R
L
R
L
L
R
L
R
R
L
L
L
L
L
L
L
L
R
R
L
R
0
20
20
30
-20
10
0
-30
0
20
-30
30
-10
30
-10
30
20
-30
-20
10
0
-20
10
-20
10
-30
30
10
-10
-20
20
-30
-10
-10
0
80
L
L
L
L
L
L
L
R
L
L
R
L
R
L
R
L
R
R
R
R
R
R
L
R
L
R
L
L
R
L
L
R
R
R
R
0
-10
-10
-30
20
-20
-10
10
30
-30
10
-20
10
-20
0
10
-20
-30
20
30
-10
30
-10
30
-30
20
0
-30
0
10
-20
30
20
20
0
R
R
L
R
L
R
R
L
L
R
L
R
L
R
L
L
L
L
L
L
R
L
L
L
R
L
L
R
L
L
L
L
L
L
L
APPENDIX B
81
Table B.1 The list of color combinations and psychometric curves of Phase 1.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Object Color
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
blue
blue
blue
blue
blue
blue
blue
blue
blue
Blue
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
Gray
gray
gray
Colored Background Pairs
warm white light
blue light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
blue light
cool white light
green light
cool white light
red light
blue light
green light
blue light
red light
red light
green light
warm white light
orange light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
orange light
cool white light
green light
cool white light
red light
orange light
green light
orange light
red light
red light
green light
warm white light
blue light
warm white light
orange light
warm white light
green light
warm white light
red light
warm white light
cool white light
cool white light
blue light
cool white light
orange light
cool white light
green light
cool white light
red light
orange light
blue light
orange light
green light
orange light
red light
blue light
green light
blue light
red light
red light
green light
82
Figure B.1 Psychometric curves for the combinations (Follow according to Table B.1).
1.
2.
83
3.
4.
5.
84
6.
7.
8.
85
9.
10.
11.
86
12.
13.
14.
87
15.
16.
17.
88
18.
19.
20.
89
21.
22.
23.
90
24.
25.
26.
91
27.
28.
29.
92
30.
31.
32.
93
33.
34.
35.
94
APPENDIX C
95
Table C.1 The list of color combinations and psychometric curves for Phase2.
Participant
no
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
1
1
2
2
3
3
3
4
4
4
4
5
5
6
6
7
7
8
8
9
9
9
10
10
10
11
11
11
12
12
13
13
13
14
14
14
Object color
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
orange
blue
blue
blue
blue
blue
blue
blue
blue
blue
blue
blue
blue
blue
gray
gray
gray
gray
gray
gray
gray
gray
Colored Background Pair
cool white light
blue light
cool white light
green light
cool white light
green light
cool white light
red light
cool white light
blue light
cool white light
green light
cool white light
red light
warm white light cool white light
cool white light
blue light
cool white light
green light
cool white light
red light
warm white light cool white light
red light
green light
warm white light cool white light
red light
green light
cool white light
green light
cool white light
orange light
warm white light cool white light
cool white light
green light
warm white light cool white light
cool white light
orange light
cool white light
red light
cool white light
orange light
cool white light
red light
red light
green light
warm white light cool white light
cool white light
green light
red light
green light
warm white light cool white light
cool white light
blue light
cool white light
blue light
cool white light
orange light
red light
green light
cool white light
green light
cool white light
red light
red light
green light
96
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
15
15
15
16
16
16
16
17
17
17
17
14
18
19
13
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
gray
blue
blue
gray
warm white light
cool white light
cool white light
cool white light
cool white light
cool white light
orange light
cool white light
cool white light
red light
orange light
orange light
cool white light
red light
warm white light
cool white light
green light
red light
orange light
green light
red light
blue light
blue light
orange light
green light
blue light
blue light
red light
green light
cool white light
Figure C.1 Psychometric curves for the combinations (Follow according to Table C.1).
97
1.
2.
3.
98
4.
5.
6.
99
7.
8.
9.
100
10.
11.
12.
101
13.
10.
14.
11.
15.
12.
102
16.
17.
18.
103
19.
20.
21.
104
22.
23.
24.
105
25.
26.
27.
106
28.
29.
30.
107
31.
32.
33.
108
34.
35.
36.
109
37.
38.
39.
110
40.
41.
42.
111
43.
44.
45.
112
46.
47.
48.
113
49.
50.
51.
114
APPENDIX D
115
Statistical results of the Experiment
Table D.1.Univariate analysis of variance
Tests of Between-Subjects Effects
Dependent
Variable:Value
Type III Sum
Source
Corrected
Model
of Squares
Mean
df
Square
F
Sig.
Partial Eta
Noncent.
Observed
Squared
Parameter
Powerb
2549,522a
16 159,345
2,971 ,004
,583
47,543 ,980
642,173
1 642,173
11,975 ,001
,260
11,975 ,919
115,972
8
,971
,060
2,163 ,120
Intercept
O_Color *
Pair
Pair
14,497 ,270
782,892
6 130,482
2,433 ,046
,300
14,599 ,746
O_Color
1483,602
2 741,801
13,833 ,000
,449
27,666 ,997
Error
1823,254
34 53,625
Total
5381,505
51
4372,776
50
Corrected
Total
a. R Squared = ,583 (Adjusted R
Squared = ,387)
b. Computed using alpha = ,05
116
Table D.2. Post Hoc Tests – Object homogenous subsets
Means for groups in homogeneous subsets are displayed.
a. Uses Harmonic Mean Sample Size = 16,579.
b. Alpha = ,05.
Table D.3. Post Hoc Tests – Pair homogenous subsets
Means for groups in homogeneous subsets are displayed.
a. Uses Harmonic Mean Sample Size = 16,579.
b. Alpha = ,05
117
Figure D.1. Interaction table of object color and background hue pairs
118
APPENDIX E
119
120
Table E.1. Data for first and second phase of the experiment with differences and significances of the color combinations.
General Presentation of Data
121
between background pairs and significances are mentioned.
phase. For each participant, plot numbers from Appendices D and E are defined and for each participant the differences
or „+‟ according to its significance for the three participants from the second phase and one participant from the first
Notes: In the table, significant and not significant parts are shown for each color combination. The effect is shown as „-„